Republican state Senate Majority Leader John Flanagan will insist that more charter schools be allowed to open in New York City as part of any deal to extend Mayor de Blasio’s authority over the public-school system, The Post has learned.

“We continue to believe that every child deserves a first-rate education. This is an opportunity to take a global look at the education system in New York City,” said a source close Flanagan.

“Charter-school expansion has to be part of the discussion. Opportunities to open new charter schools will be part of the discussions on extending mayoral control,” the Flanagan insider said.

De Blasio’s office on Sunday said the mayoral control law, which expires in June, should be extended on its merits — and not linked to other issues.

“Mayoral control is a proven governance model that stands on its own. Under Mayor de Blasio, we’re seeing record high graduation rates, record low drop-out rates and rising test scores. We cannot afford to go back,” said spokeswoman Freddi Goldstein.

The city is coming close to hitting its charter-school cap — only 30 more can be approved.

There are currently 216 charter schools in the city serving 106,600 students, or 10 percent of the public-school population.

Gov. Cuomo proposed lifting the cap to allow for charter-school expansion in his executive spending proposal, but it was stripped from the state budget.

The Legislature has raised the statewide cap twice, in 2007 and 2010. The limit is 406 charters.

But there is a regional limit for New York City, where demand is strongest, within the statewide cap. The regional cap was amended in 2015 to reassign more charters within the cap to the city — but that number is dwindling.

In the past few years, the Legislature has only allowed one year extensions of mayoral control because of bad blood with de Blasio. Former Mayor Mike Bloomberg got six-year renewals.

De Blasio led a campaign to flip control of the state Senate in 2014. The Republicans retained control and have been grappling with de Blasio ever since.